Removing new line after a particular text via bash/awk/sed/perl

Question

I would like to remove all the newline character that occurs after a partiular string and replace it with a tab space. Say for instance my sample.txt is as follows

Answer 1

This might work for you:

echo -e "foo\nbar bar bar bar some text"| sed '/foo$/{N;s/\n/\t/}'
foo     bar bar bar bar some text

Actually:

echo -e "foo\nbar bar bar bar some text"| sed '/foo$/N;s/\n/\t/'
foo     bar bar bar bar some text

The latter solution is less efficient but not by much!